Suture anchor assembly and methods

ABSTRACT

A suture anchor assembly is described which includes an elongated insertion stem and an approximately cylindrical anchoring element having an axial channel for receiving the insertion stem. In its nonexpended state, the anchoring element can be placed into a pre-filled opening in a bone. An expander element loaded onto the insertion stem is engaged with a proximal end of the anchoring element. The proximal end of the anchoring element is capable of telescoping movement over the distal end of the expander element so that resilient proximal portions of the anchoring element are forced outward against the expander element, causing the resilient proximal portions of the anchoring element to expand into the bone hole, fixing the anchoring element in a pressure fit firmly within the opening. A kit for emplacing and removing the suture anchor is also provided as well as methods for attaching a suture to a bone using the present assembly.

This application is a continuation in part of copending, commonlyassigned U.S. patent application Ser. No. 08/337,944, filed Nov. 10,1994, the teachings of which are incorporated herein by reference. Thisapplication is also a continuation in part of U.S. patent applicationSer. No. 08/568,348, filed Dec. 6, 1995, which is still pending andincorporated herein by reference.

A variety of techniques are available for affixing objects such as softtissue to bone. The oldest technique utilizes thread passed through thebone and the tissue to sew the tissue down to the bone. Many sizes,shapes and types of suture and suture needles are available toaccomplish this task. Today, this method is still used for repair oftendons and ligaments in older osteoarthfitic patients, although passinga suture through bone is generally difficult and tedious.

Soft tissue repairs also have been accomplished with metal screws orstaples that attach soft tissue to bone. Metal screws and/or staplesare, however, subject to corrosion and consequent loss of structure.Moreover, the presence of metal in an anatomical site can interfere withimaging and diagnostic or therapeutic treatments near the site. Forexample, any metal implants may have to be removed by surgery prior tomagnetic resonance imaging. Patient sensitivity to nickel ions andstainless steel implants has fueled a growing controversy regarding theuse of materials containing high quantities of nickel includingnickel-titanium alloys such as Nitinol. Also, it is almost impossible toadjust the compression exerted by screws and staples on soft tissue.Thus, these devices are not fully satisfactory for soft tissue repair.

Other devices employ a suture anchor installation affixed to an arc ofwire or a plurality of barbs disposed on an outer surface of the sutureanchor body. The barbs or arc of wire are set into a bone by applyingtraction to the suture. Unfortunately, it is not always possible toposition the anchor at a precise location within a bone if an anchor isbeing drawn upwards in a bone hole by applying tension to a suture.Furthermore, many of the fastening devices require some type of impactor impulse to set the fastener in position. Impact emplacement orsetting of bone/suture anchors may result in injury to the patient aswell as placing unnecessary strain on the bone/suture fastener itself.This is especially problematic when suture anchors are intended to beplaced in soft bone such as in procedures to repair anterior cruciateligaments or repair torn rotator cuffs.

SUMMARY OF THE INVENTION

One embodiment of the invention is an anchoring device to affix a suturein a bone. The suture anchor includes an expander element havingproximal and distal ends, the distal end for engagement with a proximalend of an anchoring element. The anchor also includes an anchoringelement for insertion into a bone hole, the element being adapted formovement within the bone hole from a first position, where a proximalend of the insertion element is in facing relationship to the distal endof the expander element, to a second position, where the anchoringelement moves proximally within the bone hole so that its proximal endtelescopes over the distal end of the expander element, forcing theproximal end of the anchoring element into a wall of the bone hole. Theanchor further includes means for moving the anchoring element from thefirst to the second position.

In a further embodiment, the device includes a tubular anchoring elementfor engagement with a hole drilled in a bone that has opposed proximaland distal ends connected by way of a central longitudinal axis. Theelement has defined between the ends an axial channel extending from theproximal end of the element to the distal end of the element and havinginner and outer peripheral surfaces forming a wall between the surfaces.The wall further has defined in it a series of axially-oriented slotsbeginning at the proximal end and extending distally. A suture retaineris engaged with the anchoring element. The anchoring element furtherincludes a plurality of wall sections that are defined between theaxially-oriented slots. Proximal ends of the wall sections include afirst camming surface for mating with another camming surface on anexpander element so that the first camming surface is arranged fortelescoping movement over the other camming surface to expand the wallsections into the bone.

The invention also encompasses an anchoring device to affix a suture ina bone that includes a tubular anchoring element having opposed proximaland distal ends and an axial channel extending from the proximal end ofthe element to the distal end of the element. The anchoring element hasseveral flexible wall sections that are adapted for movement from afirst position, where the flexible wall sections are arranged along theouter peripheral surface of the element, to a second position, whereproximal ends of the flexible wall sections are forced to obliquelyexpand outwardly into a wall of the bone hole. A suture retainer is alsoengaged with the element. Preferably, the wall sections are moreflexible at their respective proximal ends than at their respectivedistal ends. Other embodiments of the anchoring element include thosehaving screw threads disposed on the distal end at an inner peripheralsurface.

The invention also pertains to a suture anchor assembly. The assemblyincludes an insertion stem having proximal and distal ends, the distalend for engagement with a distal end of a tubular anchoring element; atubular anchoring element of the invention; and a tubular expanderelement having an axial channel defined between the proximal and distalends. The expander element is adapted for loading onto the stem and hasa distal end designed to engage with the proximal end of the tubularanchor element. The anchor element is adapted for movement from a firstposition, where its proximal end is engaged with the distal end of theexpander element, to a second position, so that the tubular anchorelement telescopes over the distal end of the expander element and theflexible wall sections of the anchoring element expand into a wall ofthe bone hole. Most preferably, the insertion stem includes a frangiblesection adjacent to its distal end and designed to break when sufficienttension is applied to the stem The proximal end of the expander elementmay include a peripheral flange integral with the proximal end. Includedat the distal end of the expander and the proximal end of the flexiblewall sections are camming surfaces adapted to engage with each other inorder to expand the wall sections into the bone.

The preferred assembly of the invention also includes a tool forremoving the anchor element once the anchor element is deployed in bonehole and a tool for applying tension to the insertion stem.

A kit for deploying a suture anchor in a bone hole includes the sutureanchor assembly of the invention, a drill, a drill guide, a deploymentdevice, and a tool for removing the anchor element once deployed.

Methods for deploying a suture anchor in a bone hole are described andinclude providing an anchoring element of the invention for insertioninto an opening in a bone and engaging the anchoring element with aninsertion stem. Next, an expander element is engaged with the insertionstem so that a distal end of the expander element is engaged with aproximal end of the anchoring element. The insertion stem with itsloaded anchoring element is placed into the bone hole and the expanderelement is fixed in position in the bone hole. A tensional force isapplied to the insertion stem so that the proximal end of the anchoringelement telescopes over the distal end of the expander element and anouter surface of the anchoring element engages with the bone. Theinsertion stem is then released from the anchoring element. Mostpreferably, the step of releasing includes activating a frangiblesection of the insertion stem so that it breaks.

It is an object of the present invention to provide a suture anchor ofsimple design and construction.

It is another object of the present invention to provide a suture anchorhaving one or more bioabsorbable components.

It is yet another object of the present invention to provide anapparatus for emplacing a suture anchor in a bone that does not requirean impact or impulse in order to deploy the anchor.

It is another object of the present invention to provide a method foremplacing a suture anchor that can be used in soft bone and can beremoved from the soft bone after deployment.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description of the preferred embodiments serves inconjunction with the drawings to explain the invention in furtherdetail, in which:

FIG. 1 is an exploded view of a suture anchor of the invention;

FIG. 2 is a partial cut-away view through the suture anchor of FIG. 1emplaced in a bone hole;

FIG. 3 is a plan view of the embodiment of FIG. 2;

FIG. 4 is a partial cut-away view through the suture anchor of FIG. 1 asit is being deployed in a bone hole;

FIG. 5 is a partial cut-away view through the suture anchor of FIG. 4after emplacement in a bone hole;

FIG. 6 is a plan view of another embodiment of the suture anchoremplaced in a bone hole;

FIG. 7 is a partial cut-away view through a third embodiment of thesuture anchor emplaced in a bone hole;

FIG. 8 illustrates deployment of the suture anchor of FIG. 7, in whichFIG. 8A illustrates deployment of the suture anchor and FIG. 8Billustrates removal of the insertion stem from the bone hole;

FIG. 9 is a partial, cut-away view of deployment of the suture anchor ofFIG. 1 using a pop-rivet gun;

FIG. 10 is cut-away view of another embodiment of the suture anchordeployment device;

FIG. 11 is a cross-sectional view of a hand-held deployment means usedwith the device of FIG. 10;

FIG. 12 is a cut-away view of a device and method for removing thesuture anchor of the present invention;

FIG. 13A is an exploded view of a preferred suture anchor device of theinvention;

FIG. 13B depicts the suture anchor of FIG. 13A partially assembled;

FIG. 14 depicts in cross-section a preferred anchoring element of thesuture anchoring device of FIG. 13A; and

FIG. 15 depicts in side view a preferred expander element of the sutureanchoring device of FIG. 13A.

DETAILED DESCRIPTION OF THE INVENTION

The suture anchor assembly, according to the invention, generallyincludes an elongated insertion stem and an approximately cylindricalanchoring element having an axial channel for receiving the insertionstem. In its nonexpended state, the anchoring element can be placed intoa pre-drilled opening in a bone. An expander element is engaged with aproximal end of the anchoring element. The term "proximal" refers to apoint that is spaced-apart from the bottom of a bone hole in a directiontowards the point of origin of the assembly (i.e. towards the surgeon),as opposed to a "distal" point that is closer to the bottom of the bonehole (i.e. farthest from the point of origin; the surgeon). Theanchoring element is capable of moving proximally within the bone hole(i.e. towards the bone surface) so that the proximal end of theanchoring element telescopes over a distal end of the expander element.As a result of this movement, resilient proximal portions of theanchoring element are forced outward against the expander element,causing the resilient proximal portions of the anchoring element toexpand into the bone hole, fixing the anchoring element in a pressurefit firmly within the opening. The term "telescopes" has its commonlyunderstood meaning in this context and refers to surfaces that slideagainst each other in which one surface is forced into another. Inparticular, the distal end of the expander is forced into the proximalend of the moving anchoring element.

A. The Insertion Stem

FIG. 1 illustrates an exploded view of one embodiment of the sutureanchor assembly of the invention containing an insertion stem onto whichis loaded an anchoring element and an expander element.

One component of the suture anchor assembly 10 is an insertion stem 12,an elongated cylinder having distal 14 and proximal 16 ends. Distal end14 is preferably formed as a shoulder 15 designed to engage a distal end24 of an anchoring element 20. The insertion stem 12 has a frangibleportion 18 disposed some distance proximal to end 14. The term"frangible" refers to a portion of stem 12 that is breakable or fragile.In particular, FIG. 1 illustrates frangible portion 18 as a section ofstem 12 having a thinner diameter than the remainder of the stem. Thefrangible section 18 is designed to sever or break when sufficienttension is applied to the stem 12 in a proximal direction (shown byarrow A) that is parallel to longitudinal axis (B--B) of the stem. Thefrangible portion, however, may be other than a thin-walled section ofstem 12 and may include a series of spokes or webbing or a plurality ofvery attenuated membranes.

B. The Anchoring Element

Anchoring element 20 is substantially tubular, having opposed proximal22 and distal 24 ends connected by way of a central axial channel 26extending from the proximal end 22 of element 20 to the distal end 24 ofthe element. Distal end 24 is engaged with shoulder 15 of stem 12.Element 20 has inner 28 and outer 30 peripheral surfaces forming a wall.Defined in the wall, and in communication with axial channel 26, are aseries of axially-oriented slots 34 that begin at the proximal end 22and extend some distance towards the distal end 24.

Each of the series of axially-oriented slots 34 in the anchoring element20 define a flexible wall section 33 located between each slot. Eachwall section 33 is more flexible at its respective proximal end, in partbecause the wall section is defined between slots that extend directlyfrom the proximal end 22 of the anchoring element. The distal ends ofthe respective wall sections 33 are co-extensive with the distal end 24of anchoring element 20.

FIG. 1 also illustrates a suture retainer 48 located adjacent the distalend 24 of anchoring element 20. Suture retainer 48 is most preferably anaperture for receiving an intermediate portion of a suture (i.e. asegment between the free ends of the suture). This allows the anchoringelement to be a so-called "slidable" suture anchor. The suture retainermay be configured in a variety of other ways, including any number ofsuture retaining configurations, such as a slit, a groove, a clip orwire and the like (e.g., suture engaging slot 221 of stem 212, describedabove).

C. The Expander Element

Expander element 35 is substantially tubular, having opposed proximal 38and distal 40 ends connected by way of a central axial channel 36, theaxial channel defining a longitudinal axis (D--D). The respective innerdiameters of the expander element 35 and anchoring element 20 are ofsufficient size to allow them to be loaded onto stem 12, anchoringelement 20 being engaged first, so that proximal end 22 of the anchoringdement 20 is engaged in facing relationship to distal end 40 of expanderelement 35.

This is shown in FIG. 2 which illustrates in partial cross-section theconfiguration resulting when anchoring element 20 and expander element35 are disposed by way of stem 12 into a hole 41 drilled in a bone 42.The proximal end 22 of each of the flexible wall sections 33 has acamming surface 44 that is designed to mate with a corresponding cammingsurface 46 at the distal end of the expander element 35. The cammingsurface 46 of expander element 35 is preferably tapered or beveled, thetaper ranging from about 10 degrees to about 45 degrees, relative toaxes (B--B) and (D--D). Most preferably, the tapered camming surface isat an angle of about 30° degrees relative to these longitudinal axes.Corresponding tapered camming surfaces 44 of the anchoring element 20are also disposed at the proximal end 22 of wall sections 33.

FIGS. 3 and 4 illustrate operation of this embodiment of the sutureassembly and the forces imposed on the components of the assembly inorder to set the suture anchor into a bone hole 41. Expander element 35is substantially fixed at the bone surface 47 and this may beaccomplished by using an expander element 35 containing a flange 50 thatis integral with the proximal end 38 of element 35 and extendingradially outwardly around the periphery of the proximal end 38. In thisembodiment, flange 50 serves as a support/countersink to brace theexpander element 35 against the bone surface 47 and against a housing 57of the stem 12 (Shown in FIG. 4) to provide a solid surface onto which aforce is exerted that is opposite to the tension force applied to stem12.

When tension is applied to stem 12 (in the direction shown by arrow A),the stem 12 and anchoring element 20 are forced in the indicateddirection (i.e. proximal to the bone hole) but the expander element 35remains substantially immobile within the bone hole 41 as the result ofa distally-applied counterforce (arrow X) exerted against flange 50 by adistal end 59 of the stem housing 57 (See also FIG. 6). A proximallydirected force that is substantially equal in magnitude and in directionto the stem tension force (arrow A) is applied to the proximal end ofanchoring element 20. The anchoring element moves proximally in the bonehole and camming surfaces 44, 46 are forced into mating engagement.

As shown in FIG. 4, anchoring element 20 telescopes over thesubstantially fixed expander element 35. In the embodiment illustrated,distal camming surfaces 46 of expander element 35 remain substantiallyfixed in position within the bone hole and proximal camming surfaces 44of anchoring element 20 are forced to ride over them.

Wall sections 33 defined between the series of axially-oriented slots 34are flexible and will expand into the bone when the camming surfaces aremutually engaged and the anchoring element 20 telescopes over theexpander element 35 when tension is applied to the stem 12. Wallsections 33 have proximal ends that are more flexible then otherportions thereof. As a result, expansion of the wall sections 33 by thetelescoping movement of the anchoring element 20 over the fixed expanderelement 35 results in the wall sections 33 having a substantiallyarcuate cross section when fully deployed and expanded in the bone, theproximal ends of the wall sections being driven radially outward and inan oblique direction (i.e., at an angle relative to the longitudinalaxis of the stem). The frangible portion 18 of stem 12 is adapted tobreak when the flexible wall sections are in their fully expandedposition. Once severed, the stem 12 may be removed from the rest of theassembly, leaving the anchoring element 20, expander element 35 andattached suture (not illustrated) locked in the bone hole (See FIG. 5).The frangible portion 18 of insertion stem 12 is preferably located at adistance above the distal end 14 of the stem so that, when the stem isremoved, the remaining severed stub of the insertion stem does notextend above the level of the bone surface 47.

In other embodiments of the invention, expander element 35 need not havea proximal flange 50. FIG. 6 is a partial, plan section of a bone hole41 into which a non-flanged expander element 35 is disposed. The distalend 59 of stem housing 57 is wide enough so that it is partiallycoextensive with the bone hole 41 opening and thus simultaneouslycontacts both the bone surface 47 and proximal end 38 of expanderelement 35. Functionally, this configuration may be considered similarto that of FIG. 3 because engagement of proximal end 38 of expanderelement 35 and the distal end 59 of stem housing 57 also serve to set upa counterforce (arrow E) in opposition to the tension force applied tothe insertion stem 12, the counterforce sufficient to fix element 35 inposition within bone hole 41.

In further embodiments, illustrated in FIG. 7, distal portions ofinsertion stem 12 may include screw threads 52 for mating engagementwith corresponding screw threads 54 on the inner surface 28 of anchoringelement 20. Stem 12 includes a proximal slot 49 for engagement with ascrewdriver. Expander element 35 may include proximal flange 50 and stem12 is rotatable within the expander 35. Expander element 35 iscountersunk into the bone so that flange 50 rests upon a shoulder 51defined in the wall 53 of the bone hole 41. The screw threads 52,54provide for positioning of the anchoring element 20 in the hole 41 atits desired depth and for applying a desired telescoping force to theanchoring element by turning the insertion stem 12 into the axialchannel 26 of the anchoring element 20. In such a turnable screw threadconfiguration, illustrated in FIG. 8A, as the threaded insertion stem 12is turned clockwise, the expander element 35 remains fixed in the bonehole 41 by way of counterforce pressure against flange 50, but theproximal end 22 of anchoring element 20 is forced to telescope over thedistal end 40 of expander element 35 as the threads on the insertionstem axe turned. Camming surfaces 44,46 engage and flexible wallsections 33 are expanded into the bone 42. Once the anchoring element isfixed into the bone, the stem and expander may be released by backingout the threaded stem (See FIG. 8B).

In another embodiment of the assembly, the distal end 14 of insertionstem 12 and the distal end 24 of anchoring element 20 are attached as anintegral unit so that only the expander element 35 need be loaded ontothe insertion stem. Alternately, the assembly may comprise the integralanchoring element and insertion stem and an expander element that ismolded to, or extruded integrally with, a distal end of a housing asdescribed below with reference to FIG. 9.

The component parts of the suture anchor assembly may be fabricated byconventional molding or extrusion procedures. Element 20 is preferablyconstructed of a biocompatible material. The term "biocompatible" meansthat the anchoring element material is chemically and biologicallyinert. Suitable materials for the anchoring element include, forexample, an implant grade high density polyethylene, low densitypolyethylene (PE 6010 and PE 2030); acetal (trademark "Delrin",manufactured by Dupont Chemical Co.) and polypropylene (13R9A and 23M2:all made by Rexene, Dallas, Tex.). Of these, PE 6010 and 13R9A have beenFDA listed as class 6 materials.

The anchoring element may also be bioabsorbable. The term"bioabsorbable" refers to those materials that are meant to bedecomposed or degraded by bodily fluids, such as, for example, blood andlymph. The anchoring element is preferably made from a biodegradablepolymer or copolymer of a type selected in accordance with the desireddegradation time. That time in turn depends upon the anticipated healingtime of the tissue which is the subject of the surgical procedure. Knownbioabsorbable polymers and copolymers range in degradation time fromabout 3 months for polyglycolide to about 48 months forpolyglutamic-co-leucine. A common bioabsorbable polymer used inabsorbable sutures is poly (L-lactide) which has a degradation time ofabout 12 to 18 months. The preferred anchoring element is comprised ofan absorbable copolymer derived from glycolic and lactic acids, such asa synthetic polyester chemically similar to other commercially availableglycolide and lactide copolymers. Glycolide and lactide degrade andabsorb in the body by hydrolysis into lactic acid and glycolic acidwhich am then metabolized by the body.

The following Table set forth below lists polymers which are useful forthe bioabsorbable material employed for the anchoring element, and otherparts of the bone fastener as described below. These polymers are allbiodegradable into water-soluble, non-toxic materials which can beeliminated by the body. Their safety has been demonstrated and they arelisted as approved materials by the U.S. Food and Drug Administration.

                  TABLE                                                           ______________________________________                                        Polycaprolactone       Poly (L-lactide)                                       Poly (DL-lactide)      Polyglycolide                                          95:5 Poly (DL-lactide-co-glycolide)                                                                  Polydioxanone                                          Polyesteramides                                                               Copolyoxalates                                                                Polycarbonates                                                                Poly (glutamic-co-leucine)                                                    90:10 Poly (DL-lactide-co-glycolide)                                          85:15 Poly (DL-lactide-co-glycolide)                                          75:25 Poly (DL-lactide-co-glycolide)                                          50:50 Poly (DL-lactide-co-glycolide)                                          90:10 Poly (DL-lactide-co-caprolactone)                                       75:25 Poly (DL-lactide-co-caprolactone)                                       50:50 Poly (DL-lactide-co-caprolactone)                                       ______________________________________                                    

D. Apparatus for Deployment

A preferred deployment apparatus of the invention retains the insertionstem, expander element and anchoring element prior to emplacement andincludes a tool for exerting tension on the insertion stem. Thepreferred apparatus also allows for separating the insertion stem andexpander element from the anchoring element after the frangible sectionis severed.

FIG. 9 is a partial, plan view illustrating one embodiment of adeployment apparatus of the invention and its mode of operation. Theinsertion stem 12 is preloaded with the anchoring element 20 and theexpander element 35 and the stem 12 is then placed into an apparatussimilar to a pop-rivet gun 56. The stem 12 is encased within a housing57 of the apparatus so that a toothed collet 58 or other similargrasping means engages the insertion stem 12. The anchor assembly isthen placed in a hole 41 drilled into a bone 42 and a distal end 59 ofthe housing 57 is pressed into contact with the bone surface 47. Thishelps fix the flange 50 of expander element 35 into position at the bonesurface 47. Activation of the apparatus 56 retracts the insertion stem12 proximally (arrow A) to induce tension on the stem. The cammingsurfaces 44,46 of the respective anchor 20 and expander 35 elements comeinto telescoping contact and the flexible wall sections 33 of anchoringelement 35 are set into the bone 42. Tension is continually exerted onstem 12 until the stem shears off from the remainder of the sutureassembly at the frangible section 18. In those embodiments of theapparatus in which expander element 35 is molded or extruded integrallyas one-piece with distal end 59 of housing 57, once the stem is shearedthe rest of the stem and the expander element are removed to leave theanchoring element with its attached suture (and severed stem) in thebone. In the other embodiments where the expander element is notintegral with the housing, the severed stem and the expander element areleft in the bone.

FIG. 10 illustrates another embodiment of an emplacement apparatus ofthe invention and its mode of operation. The apparatus includes ahousing 57 which encloses insertion stem 12 held co-axially in place bya toothed collet 58. The proximal end 60 of the housing 57 is engagedwith arms 90 of a push rod 92 in the shape of an inverse T. Proximal end60 of housing 57 also includes an aperture (not shown) for receiving thecollet 58. The collet 58 is integral with a bayonet-type connector 64that allows the combined connector and housing to be removably attachedto a hand held means 120 (See FIG. 11). The stem 12 is thus co-axiallyarranged around the collet 58 and the collet can move co-axially withinthe housing 57. The anchoring element 20 and expander element 35 arethreaded on the stem and the stem 12 is positioned in the collet.

Referring now to FIG. 11, the hand-held means 120 is of similar designto the hand held means described in co-pending and commonly assignedpatent application Ser. No. 08/163,130, "Bone Fastener", pending, filedDec. 6, 1993, incorporated herein by reference. Briefly, the hand heldmeans 120 consists of two handle elements 122, 124 slidably engaged toprovide a comfortable pistol grip 126 by which handle element 124 can bemoved in a proximal-distal direction with respect to the handle element122 by squeezing the pistol grip 126. The distal end 123 of the handleelement 122 is adapted for removably mounting the bayonet connector 64.The distal end 125 of handle element 124 includes a rod 129 whose distalend 127 abuts push rod 92 when the handle elements are assembled and theconnector 64 is mounted onto end 123 of handle element 122.

With the apparatus so assembled, the surgeon grasps the apparatus by thepistol grip 126, and directs the anchoring assembly into the predrilledhole in the bone. The distal end 59 of the housing 57, and optionallythe flange 50 of the expander element, engage the bone surface. Then,the surgeon squeezes the grip 126 sliding the handle 124 frontward withrespect to the handle element 122, as indicated by the arrow 131. Rod129 presses against push rod 92 in the distal direction (arrow X in FIG.10) and the downward force is transmitted through the inverse-T arms 90to the housing 57 and against the bone surface 47. At the same time, theconnector 64 and attached co-axially moveable stem 12 are urgedproximally (arrow A), translating the distal force on the push rod 92 toa proximal, tensioning force on the insertion stem 12.

E. Apparatus for Removal

A significant feature of the present suture assembly is that the anchorelement may be removed after deployment by forcing the anchoring elementdistally back down into the bone hole 41. A removal apparatus asillustrated in FIG. 12 consists of a cannulated rod 60 whose distal end62 is adapted to engage with distal end 24 of anchoring element 20 orwith the severed end of the insertion stem 12 at the frangible section.As illustrated, rod 60 is engaged with anchoring element 20 and presseddistally (arrow F) to drive the anchor element 20 back down into thebone hole until the flexible wall sections 33 are substantially parallelto the longitudinal axis (F--F) of the bone hole and extend in aproximal -distal direction. A sheath 64 is then slid (arrow G) over therod 60 to engage outer peripheral surfaces of the anchoring element 20.This engagement may be facilitated by a series of detents (not shown)located on the distal end 65 of sheath 64 which fixedly engages theanchoring element. The anchoring element, any insertion stem remaining,and sheath are removed (arrow H) from the bone hole as a unit.

F. Methods

One method, although by no means the only method, for attaching softtissue to bone will be described below.

To attach soft tissue to bone, a surgeon takes the sharpened proximalend of a K-wire (manufactured, for example, by Kirschner MedicalCompany) and spears the tissue that is to be attached. The proximal endof the K-wire is then placed over the bone surface at the approximatesite of attachment. The K-wire is then drilled into the bone at thatsite. If the location is where the surgeon wants it, the surgeon thenthreads a cannulated drill of the appropriate size over the K-wire. Ahole is then drilled into the bone using the cannulated drill. Thendrill and K-wire is are removed. It will be understood that the use of aK-wire is not essential to this method of drilling a bone hole.

Whether or not the K-wire is used, the suture assembly of the inventionis then loaded within an emplacement apparatus (for example, describedabove with reference to FIGS. 9-11). The assembly is pressed downwardsthrough the tissue and into the bone hole so that the anchoring elementis emplaced into the bone hole. If the surgeon decides that theorientation of the assembly and soft tissue is correct, the emplacementapparatus is triggered by applying a tensional force to the insertionstem so that the proximal end of the anchoring element telescopes overthe distal end of the expander element. The outer, flexible surfaces ofthe anchoring element engage with the bone and the insertion stem isreleased from the anchoring element to set the anchor element within thebone hole. The apparatus is removed. Other variations on this techniqueinclude first drilling a bone hole and then punching a hole through thesoft tissue. The tissue is then moved over the bone hole using, forexample, a K-wire or a suture passer grasping device.

It is an important feature of the present invention that the forceneeded to telescope the anchoring element may be substantiallycontinuous and spread out over time. The anchoring element is telescopedover the expander element with a compressive motion that is axiallydelivered in a direction substantially parallel to the longitudinal axisof the insertion stem. Thus, the apparatus for deploying the presentassembly requires an advancing drive mechanism which lacks any impact orimpulse characteristics.

The components of the bone fastener of the invention may be included ina surgical fastener kit. An exemplary kit may include an anchoringelement of the invention; an insertion stem of the invention and aholder for engaging with the anchoring element, the holder capable ofmaintaining the anchoring element in position with the bone opening.Other embodiments of the kit may include a grasper/manipulator forgrasping free ends of the suture to pass the suture through soft tissue.Such a suture-grasping device is described in commonly assigned andcopending application Ser. No. 08/097,154, filed Jul. 26, 1993, pending,incorporated herein by reference. A K-wire, drill and drill guide mayalso be also included. Preferably, the kit is encased in a sterile trayor other receptacle for use by an operator at a site.

The invention will now be illustrated by the following non-limitingexamples.

Three different polysulfone anchor elements were fabricated by machiningpolysulfone, extruded bar stock. The elements included several of 2.8 mmlength (wall thickness of 0.018, 0.024 and 0.035 inches); 3.5 mm long(0.018" wall thickness) and 3.8 mm long (0.025" wall thickness). Anchorswere attached to sutures and were set using the procedures describedherein into an artificial bone made of open-cell foam made by Sawbones,Inc., P. O. Box 589, Vashon, Wash., 98070. Tension was applied to thesutures by a stainless steel hardened wire attached to the back of theanchor. Tension was measured by a force gauge. The foam/suture assemblywas observed for anchor failure. Results are presented below in theTable.

    ______________________________________                                        Diameter                                                                             Wall     Force                                                         (mm)   (inches) (lb)    Observations                                          ______________________________________                                        2.8    0.018    29.0    Failure; 3 wall sections bent                                                 back on themselves; foam cone                                                 pulled out 0.25" diameter                                    0.024    32.8    Failure; 4 wall sections bent                                                 back on themselves; foam cone                                                 pulled out 0.23" diameter                                    0.035    33.4    Failure; 4 wall sections bent                                                 back on themselves; foam cone                                                 pulled out 0.23" diameter                             3.5    0.018    37.2    Failure; anchor broken with                                                   half pulled through; wall                                                     sections on the broken half                                                   were straight.                                               0.018    43.0    Failure; wall sections bent back                                              over themselves                                       3.8    0.025    33.0    No anchor failure; foam bone                                                  wedge pulled out and only 2 wall                                              sections were spread; foam                                                    pullout .5" diameter/.25" deep                               0.025    51.0    No anchor failure; all wall                                                   sections spread; foam bone                                                    wedge pulled out; .75:                                                        diameter/.25" deep                                    ______________________________________                                    

G. Further Embodiments

FIG. 13A depicts an insertion stem 212 according to a preferred practiceof the invention. As with the stem 12 depicted in FIG. 1 and describedin connection therewith, the stem 212 is elongate and has distal 214 andproximal 216 ends. Distal end 214 is formed with a shoulder (or head)215 designed to engage a distal end 224 of an anchoring element 220. Theinsertion stem 212 has a frangible portion 218, disposed some distanceproxima/from end 214, and designed to sever or break when sufficienttension is applied to the stem 212 in a proxima/direction parallel tolongitudinal axis of the stem. As above, the frangible portion may beother than a thin-walled section of stem 12 and may include a series ofspokes or webbing or a plurality of very attenuated membranes.

The stem 212 includes threading 217 for threaded engagement by thedeployment apparatus of FIGS. 9-11. Ridges 219, which are disposeddistal of frangible portion 218 of stem 212, provide ratchet-likeretention of the expander element 235 in the assembled suture anchorassembly, thereby preventing unwanted or excess movement of the expanderelement relative to the anchoring and insertion elements. Sutureengaging slot 221 provides a track in which a loop of a suture may beretained, thereby providing additional control over the suture, e.g.,for purposes of knot-tying.

With continued reference to FIG. 13A, like anchoring element 20 depictedin FIG. 1 and described in connection therewith, anchoring element 220is substantially tubular, having opposed proximal 222 and distal 224ends connected by way of a central axial channel (not shown) extendingfrom the proximal end 222 to the distal end 224. Distal end 224 engageswith shoulder 215 of stem 212. As above, element 220 has inner and outerperipheral surfaces forming a wall. Defined in the wall, and incommunication with the axial channel, are a series of axially-orientedslots 234 that begin at the proximal end 222 and extend some distancetowards the distal end 224. Each of the series of axially-oriented slots234 in the anchoring element 220 define a flexible wall section 233located between each slot. The anchoring element can include a pluralityof slots 234 and, thereby, a corresponding number of wall sections 233.Although the number of slots (and wall sections) can range from 2 to 10(or upwards), a preferred number of slots (and wall sections) is threeor four.

Referring to FIG. 14, the anchoring element 220 is shown incross-section. As evident in the drawing, each wall section 233 tapersgradually from a base portion 231 to the proximal end 222. That tapercan be, for example, 0° to 200 degrees and, preferably, is about 8°.Camming surfaces 244 at the tips of the walls have more pronouncedtapers. These can range, e.g., from 30° to 75° and is, preferably, about60°.

Referring to FIG. 13A, a preferred expander element 235, like element 35depicted in FIG. 1 and described in connection therewith, has opposedproximal 238 and distal 240 ends connected by way of a central axialchannel 236. The diameter of channel 236 is of sufficient size to allowit to be loaded onto stem 212, along with anchoring element 220, so thatproximal end 222 of the anchoring element 220 is engaged in facingrelationship to distal end 240 of expander element 235. This is shown inFIG. 13B, which illustrates in partial cross-section the configurationresulting when anchoring element 220 and expander element 235 are arereadied for assembly on stem 212.

The proximal end 222 of each of the flexible wall sections 233 ofanchoring element 220 has a camming surface 244 that is designed to matewith a corresponding camming surface 246 at the distal end of theexpander element 235. The camming surface 246 of expander element 235 istapered at approximately 45°, though that taper can be as little asabout 10° and as much as 60°.

To prevent the anchoring element 220 from telescoping too far over theexpander element 235, the expander element 235 includes projections orwings 237, each of which corresponds with a slot 234 of anchoringelement 220. The wings 237 slidingly engage with slots 234 as the sutureanchor system is being assembled. This permits the anchoring element 220to telescope over expander element 235 until the wings 237 reach thebottoms 229 of their respective slots 234. As a less preferredalternative, the anchoring element 220 can include an internal shoulder,or other such protrusion, that prevents the anchoring element 220 fromtelescoping too far over expander element 235.

The expander element 235 is shown in side view at FIG. 15. There, it isseen that the element 235 has a height (i.e., length along thelongitudinal axis) less than that of the sides 233 of the anchoringelement 220. Preferably, the height of element 235 is approximatelyone-half that of the sides 233 and, still more preferably, a heightsubstantially equal to that of the camming surface 244.

A further appreciation of an exemplary apparatus of the type shown inFIGS. 13A-15 may be attained by reference to the schematics shown in theAppendix filed herewith.

Equivalents

It should be understood that various changes and modifications of thepreferred embodiments may be made within the scope of the invention.Thus it is intended that all matter contained in the above descriptionbe interpreted in an illustrative and not limited sense.

In view of the forgoing, what I claim is:
 1. A suture anchoring deviceto affix a suture in a bone, comprising:a tubular anchoring element forengagement with a hole drilled in a bone, the element having opposedproximal and distal ends connected by way of a central longitudinalaxis, the element having defined therein an axial channel extending fromthe proximal to the distal end thereof, the element having inner andouter peripheral surfaces forming a wall therebetween, wherein the wallhas defined in it a plurality of axially-oriented slots beginning at theproximal end of the anchoring element and extending distally, the slotsin communication with the axial channel; and a plurality of flexiblewall sections further defined between the axially-oriented slots,wherein a proximal surface of a wall section comprises a first cammingsurface for mating with a second camming surface on an expander element,the first camming surface arranged to telescope over the second cammingsurface so that, when the anchoring element is disposed in the bone holeand moved proximally against the expander element, the flexible wallsections expand into the bone, at least one of the anchoring element andthe expander element including means for inhibiting excess movement ofthe anchoring element relative to the expander element.
 2. The sutureanchoring device of claim 1, wherein said inhibiting means comprisesatleast one projection on the expander element for sliding engagement witha corresponding slot in the wall of the anchoring element, and forpreventing movement of the anchoring element relative to the expanderelement upon abutment of the projection with a bottom of thecorresponding slot.
 3. The suture anchoring device of claim 2, whereinsaid inibiting means comprises a plurality of projections on theexpander element, each for sliding engagement with a corresponding slotin the wall of the anchoring element and for preventing movement of theanchoring element relative to the expander element upon abutment of eachprojection with a bottom of the respective slot.
 4. The suture anchoringdevice of claim 1, wherein the inhibiting means comprises a projectionon an inner surface of the anchoring element for inhibiting movement ofthe anchoring element relative to the expander element upon abutment ofthe expander element with that projection.
 5. The suture anchoringdevice of claim 4, wherein the projection is a shoulder extending atleast partially around an inner surface defined by the axial channel ofthe anchoring element.
 6. A suture anchor assembly, comprising:aninsertion stem having proximal and distal ends, the distal end forengagement with a distal end of a tubular anchoring element; a tubularanchoring element having defined therein an axial channel for loadingonto the stem and having a distal end for engagement with the distal endof the stem, the anchoring element including inner and outer peripheralsurfaces forming a wall therebetween, the wall having defined therein aplurality of axially-oriented slots in communication with the axialchannel, the slots beginning at a proximal end of the element andextending distally, wherein the plurality of slots further define aplurality of flexible wall sections disposed between adjacent,axially-oriented slots; a tubular expander element having definedtherein an axial channel, the expander element for loading onto the stemand having a distal end for engagement with the proximal end of thetubular anchor element, wherein the tubular anchor element is adaptedfor proximal movement within a bone hole from a first position, where aproximal end thereof is engaged with the distal end of the expanderelement, to a second position, where the proximal end of the tubularanchor element telescopes over the distal end of the expander element sothat flexible wall sections expand into a wall of the bone hole; and atleast one of the insertion stem, the anchoring element and the expanderelement including means for retaining a suture.
 7. The suture anchoringdevice of claim 6, wherein the suture retaining means comprises achannel in the distal end of the insertion stem.
 8. The suture anchoringdevice of claim 6, wherein at least one of the anchoring element and theexpander element include inhibiting means for preventing excess movementof the anchoring element relative to the expander element.
 9. The sutureanchoring device of claim 8, wherein said inhibiting means comprisesatleast one projection on the expander element for sliding engagement witha corresponding slot in the wall of the anchoring element, and forpreventing movement of the anchoring element relative to the expanderelement upon abutment of the projection with a bottom of thecorresponding slot.
 10. The suture anchoring device of claim 9, whereinsaid inibiting means comprises a plurality of projections on theexpander element, each for sliding engagement with a corresponding slotin the wall of the anchoring element and for preventing movement of theanchoring element relative to the expander element upon abutment of eachprojection with a bottom of the respective slot.
 11. The sutureanchoring device of claim 8, wherein the inhibiting means comprises aprojection on an inner surface of the anchoring element for inhibitingmovement of the anchoring element relative to the expander element uponabutment of the expander element with that projection.
 12. The sutureanchoring device of claim 11, wherein the projection is a shoulderextending at least partially around an inner surface defined by theaxial channel of the anchoring element.
 13. The suture anchoring deviceof claim 8, wherein the inhibiting means comprises at least oneprojection on the insertion element inhibiting movement of the expanderelement.
 14. The suture anchoring device of claim 13, wherein theinibiting means comprises at least one ridge on the insertion element ofratchet-like retention of the expander element thereon.